Groundwater monitoring wells were installed in the past by drilling a hole in the ground and lowering a slotted well casing into the hole. Filter material was then poured into the annulus between the hole and the well casing, to completely cover the slotted screen. A clay material was then placed above the filter material to effectively cap the filtermaterial. There have been a number of problems with these conventional techniques for installing groundwater monitoring wells. One problem is physical plugging of the screen, which oftentimes prevents fluid samples from entering the screened interval.
To counter this problem, other systems have been developed, including a preform which is installed directly into a bore hole as exemplified in U.S. Pat. No. 5,309,994. Contained within the preform are dry granular materials layered around the casing, and enclosed by an outer cylindrical sleeve. When the outer cylindrical sleeve is removed, the granular material disperses in ordered layers around the well casing in the bore hole. This technique avoids screen plugging, and ensures fluid sampling within the screened interval. However, these systems are slow and expensive to install. Bore hole must be drilled, and then a preform inserted. Thus, there is a need for a device which installs a sand-filter-equipped and sealed screened interval that can be used as a fluid monitoring well at any selected depth using direct-push technology, that is, technology which inserts a well assembly directly into the soil without having to drill a hole. Additionally, there is a need for installing smaller sized wells. Tools designed to be driven directly into the soil typically have smaller diameters than bits or augers which are used to drill a hole. Thus, a smaller well casing may be installed.